This project investigates the statistical problems involved in the Measurement of experimental and clinical pain. (1) A study has been conducted to investigate the statistical technique used in deriving psychophysical measurements of pain. A report has been prepared for the part of work dealing with sensory-decision-theory measures such as d' and Beta. Further study of the interrelationship among other types of measurement indices, e.g., p(A), Hodo's percent bias and MacNicol's index of response bias,B, are ongoing. (2) A study of statistical quantification of the temporal characteristics of persistent, episodic pain such as migraine headache is currently being developed. A group of measurements for this type of pain has been selected for further investigation. (3) A meeting is in preparation by the members of OBFS and other program areas of NINCDS to review the current state-of-the-art of the methodology for the measurement of pain. This meeting will justify the need for conducting a full-scale symposium to discuss various aspects of pain measurement problems.